Mu'awiyah bin Qurrah (may Allah have mercy on him) said: It is reported from al-Agharr al-Muzani (may Allah be pleased with him) that a man came to him (peace and blessings be upon him) and said: I have reached the morning and have not prayed witr? He (peace and blessings be upon him) said: "Witr is the prayer of the night." Then he (peace and blessings be upon him) said three or four times: "Stand up and pray witr."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4522